• Aiken, C., A. Moore, and J. Middleton, 2002: The non-normality of coastal ocean flows around obstacles, and their response to stochastic forcing. J. Phys. Oceanogr., 32 , 29552974.

    • Search Google Scholar
    • Export Citation
  • Alaee, M. J., G. Ivey, and C. Pattiaratchi, 2004: Secondary circulation induced by flow curvature and Coriolis effects around headlands and islands. Ocean Dyn., 54 , 2738.

    • Search Google Scholar
    • Export Citation
  • Aristegui, J., P. Sangra, S. Hernandez-Leon, M. Canton, A. Hernandez-Guerra, and J. Kerling, 1994: Island-induced eddies in the Canary Islands. Deep-Sea Res. I, 41 , 15091525.

    • Search Google Scholar
    • Export Citation
  • Barkley, R., 1972: Johnston Atol’s wake. J. Mar. Res., 30 , 201216.

  • Barton, E., G. Basterretxea, P. Flament, E. Mitchelson-Jacob, B. Jones, J. Aristegui, and F. Herrera, 2000: Lee region of Gran Canaria. J. Geophys. Res., 105 , 1717317193.

    • Search Google Scholar
    • Export Citation
  • Batchelor, G. K., 1967: An Introduction to Fluid Dynamics. Cambridge University Press, 515 pp.

  • Boyer, D. L., and P. Davies, 1982: Flow past a cylinder on a beta plane. Philos. Trans. Roy. Soc. London, 306A , 3356.

  • Boyer, D. L., and R. Chen, 1987: On the laboratory simulation of topographic effects on large scale atmospheric motion systems: The Rocky Mountains. J. Atmos. Sci., 44 , 100123.

    • Search Google Scholar
    • Export Citation
  • Boyer, D. L., and P. Davies, 2000: Laboratory studies of orographic effects in rotating and stratified flows. Annu. Rev. Fluid Mech., 32 , 165202.

    • Search Google Scholar
    • Export Citation
  • Caldeira, R. M. A., and P. Marchesiello, 2002: Ocean response to wind sheltering in the Southern California Bight. Geophys. Res. Lett., 29 .1635, doi:10.1029/2001GL014563.

    • Search Google Scholar
    • Export Citation
  • Caldeira, R. M. A., P. Marchesiello, N. P. Nezlin, P. M. DiGiacomo, and J. C. McWilliams, 2005: Island wakes in the Southern California Bight. J. Geophys. Res., 110 .C11012, doi:10.1029/2004JC002675.

    • Search Google Scholar
    • Export Citation
  • Chabert D’Hieres, G., P. A. Davies, and H. Didelle, 1989: A laboratory study of the lift forces on a moving solid obstacle in a rotating fluid. Dyn. Atmos. Oceans, 13 , 4775.

    • Search Google Scholar
    • Export Citation
  • Coutis, P., and J. Middleton, 2002: The physical and biological impact of a small island wake in the deep ocean. Deep-Sea Res. I, 49 , 13411361.

    • Search Google Scholar
    • Export Citation
  • Dietrich, D. E., M. J. Bowman, and C. A. Lin, 1996: Numerical studies of small island wakes in the ocean. Geophys. Astrophys. Fluid Dyn., 83 , 195231.

    • Search Google Scholar
    • Export Citation
  • Doglioli, A. M., A. Griffa, and M. G. Magaldi, 2004: Numerical study of a coastal current on a steep slope in presence of a cape: The case of the Promontorio di Portofino. J. Geophys. Res., 109 .C12033, doi:10.1029/2004JC002422.

    • Search Google Scholar
    • Export Citation
  • Dower, J., H. Freeland, and K. Juniper, 1992: A strong biological response to oceanic flow past Cobb seamount. Deep-Sea Res., 39A , 11391145.

    • Search Google Scholar
    • Export Citation
  • Edwards, K. A., P. MacCready, J. N. Moum, G. Pawlak, J. Klymak, and A. Perlin, 2004: Form drag and mixing due to tidal flow past a sharp point. J. Phys. Oceanogr., 34 , 12971312.

    • Search Google Scholar
    • Export Citation
  • Furukawa, K., and E. Wolanski, 1998: Shallow-water frictional effects in island wakes. Estuarine Coastal Shelf Sci., 46 , 599608.

  • Gerrard, T. H., 1978: The wake of a cylindrical bluff bodies at low Reynolds number. Philos. Trans. Roy. Soc. London, 288A , 351382.

  • Graves, P. G., J. C. McWilliams, and M. T. Montgomery, 2006: Vortex evolution due to straining: A mechanism for dominance of strong, interior anticyclones. Geophys. Astrophys. Fluid Dyn., 100 , 151183.

    • Search Google Scholar
    • Export Citation
  • Hamner, W. M., and I. R. Hauri, 1981: Effects of island mass: Water flow and plankton pattern around a reef in the Great Barrier Reef lagoon, Australia. Limnol. Oceanogr., 26 , 10841102.

    • Search Google Scholar
    • Export Citation
  • Harlan, J. A., S. E. Swearer, R. R. Leben, and C. A. Fox, 2002: Surface circulation in a Caribbean island wake. Cont. Shelf Res., 22 , 417434.

    • Search Google Scholar
    • Export Citation
  • Harrison, D. E., and A. R. Robinson, 1978: Energy analysis of open regions of turbulent flows: Mean eddy energetics of a numerical ocean circulation experiment. Dyn. Atmos. Oceans, 2 , 185211.

    • Search Google Scholar
    • Export Citation
  • Hasegawa, D., H. Yamazaki, R. G. Lueck, and L. Seuront, 2004: How islands stir and fertilize the upper ocean. Geophys. Res. Lett., 31 .L16303, doi:10.1029/2004GL020143.

    • Search Google Scholar
    • Export Citation
  • Hernandez-Leon, S., 1991: Accumulation of mesozooplankton in a wake area as a causative mechanism of the “island-mass effect.”. Mar. Biol., 109 , 141147.

    • Search Google Scholar
    • Export Citation
  • Heywood, K. J., D. P. Stevens, and G. R. Bigg, 1996: Eddy formation behind the tropical island of Aldabra. Deep-Sea Res. I, 43 , 555578.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., 1974: The role of potential vorticity in symmetric stability and instability. Quart. J. Roy. Meteor. Soc., 100 , 480482.

    • Search Google Scholar
    • Export Citation
  • Johnson, E. H., and M. Page, 1993: Flow past a circular cylinder on a β-plane. J. Fluid Mech., 257 , 603626.

  • Kolyshini, A. A., and M. S. Ghidaoui, 2003: Stability analysis of shallow wake flows. J. Fluid Mech., 494 , 355377.

  • Lin, J-T., and Y-H. Pao, 1979: Wakes in stratified fluids. Annu. Rev. Fluid Mech., 11 , 317338.

  • Lloyd, P. M., P. Stansby, and D. Chen, 2001: Wake formation around islands in oscillation laminar shallow-water flows. Part 1: Experimental investigation. J. Fluid Mech., 429 , 217238.

    • Search Google Scholar
    • Export Citation
  • Marchesiello, P., J. C. McWilliams, and A. F. Shchepetkin, 2003: Equilibrium structure and dynamics of the California Current System. J. Phys. Oceanogr., 33 , 753783.

    • Search Google Scholar
    • Export Citation
  • Martinez, E., and K. Maamaatuaiahutapu, 2004: Island mass effect in the Marquesas Islands: Time variation. Geophys. Res. Lett., 31 .L18307, doi:10.1029/2004GL020682.

    • Search Google Scholar
    • Export Citation
  • McCartney, M., 1975: Inertial Taylor columns on a beta plane. J. Fluid Mech., 68 , 7195.

  • Merkin, L. O., 1980: Flow separation on a beta plane. J. Fluid Mech., 99 , 399409.

  • Neill, S. P., and A. J. Elliott, 2004: Observations and simulations of an unsteady island wake in the Firth of Forth, Scotland. Ocean Dyn., 54 , 324332.

    • Search Google Scholar
    • Export Citation
  • Ooyama, K., 1966: On the stability of the baroclinic circular vortex: A sufficient condition for instability. J. Atmos. Sci., 23 , 4353.

    • Search Google Scholar
    • Export Citation
  • Page, M. A., 1985: On the low Rossby number of a rotating fluid past a circular cylinder. J. Fluid Mech., 156 , 205221.

  • Pattiaratchi, C., A. James, and M. Collins, 1987: Island wakes and headland eddies: A comparison between remotely sensed data and laboratory experiments. J. Geophys. Res., 92 , 783794.

    • Search Google Scholar
    • Export Citation
  • Pedlosky, J., 1987: Geophysical Fluid Dynamics. 2d ed. Springer-Verlag, 710 pp.

  • Perret, G., A. Stegner, M. Farge, and T. Pichon, 2006: Cyclone–anticyclone asymmetry of large-scale wakes in the laboratory. Phys. Fluids, 18 .036603, doi:10.1063/1.2179387.

    • Search Google Scholar
    • Export Citation
  • Pingree, R. D., and L. Maddock, 1979: The tidal physics of headland flows and offshore tidal bank formation. Mar. Geol., 32 , 269289.

  • Rissik, D., I. M. Suthers, and C. T. Taggart, 1997: Enhanced particle abundance in the lee of an isolated reef in the south Coral Sea: The role of flow disturbance. J. Plankton Res., 19 , 13471368.

    • Search Google Scholar
    • Export Citation
  • Schar, C., and D. Durran, 1997: Vortex formation and vortex shedding in continuously stratified flows past isolated topography. J. Atmos. Sci., 54 , 534554.

    • Search Google Scholar
    • Export Citation
  • Shchepetkin, A. F., and J. J. O’Brien, 1996: A physically consistent formulation of lateral friction in shallow-water equation ocean models. Mon. Wea. Rev., 124 , 12851300.

    • Search Google Scholar
    • Export Citation
  • Shchepetkin, A. F., and J. C. McWilliams, 1998: Quasi-monotone advection schemes based on explicit locally adaptive dissipation. Mon. Wea. Rev., 126 , 15411580.

    • Search Google Scholar
    • Export Citation
  • Shchepetkin, A. F., and J. C. McWilliams, 2005: The Regional Ocean Modeling System: A split-explicit, free-surface, topography-following-coordinate oceanic model. Ocean Modell., 9 , 347404.

    • Search Google Scholar
    • Export Citation
  • Shen, C. Y., and T. E. Thomas, 1998: Inertial instability of large Rossby number horizontal shear flows in a thin homogeneous layer. Dyn. Atmos. Oceans, 26 , 185208.

    • Search Google Scholar
    • Export Citation
  • Signell, R. P., 1989: Tidal dynamics and dispersion around coastal headlands Ph.D. Thesis, Woods Hole Oceanographic Institution, MIT, 162 pp.

  • Signell, R. P., and W. R. Geyer, 1991: Transient eddy formation around headlands. J. Geophys. Res., 96 , 25612575.

  • Simmons, H. L., and D. Nof, 2000: Islands as eddy splitters. J. Mar. Res., 58 , 919956.

  • Smolarkiewicz, P. K., and R. Rotunno, 1989: Low Froude number flow past three dimensional obstacles. Part I: Baroclinically generated lee vortices. J. Atmos. Sci., 46 , 11541164.

    • Search Google Scholar
    • Export Citation
  • Stansby, P. K., and P. Lloyd, 2001: Wake formation around islands in oscillation laminar shallow-water flows. Part 2. Three-dimensional boundary-layer modeling. J. Fluid Mech., 429 , 239254.

    • Search Google Scholar
    • Export Citation
  • Tansley, C., and D. Marshall, 2001: Flow past a cylinder on a beta-plane with application to Gulf Stream separation and the Antarctic Circumpolar Current. J. Phys. Oceanogr., 31 , 32743283.

    • Search Google Scholar
    • Export Citation
  • Tomczak, M., 1988: Island wakes in deep and shallow water. J. Geophys. Res., 93 , 51535154.

  • Van Dyke, M., 1982: An Album of Fluid Motion. Parabolic Press, 174 pp.

  • Walker, J. D. A., and K. Stewartson, 1972: The flow past a cylinder in a rotating frame. Z. Angew. Math. Phys., 23 , 745752.

  • Wolanski, E., and W. M. Hamner, 1988: Topographically controlled fronts in the ocean and their biological influence. Science, 241 , 177181.

    • Search Google Scholar
    • Export Citation
  • Wolanski, E., J. Imberger, and M. L. Heron, 1984: Island wakes in shallow coastal waters. J. Geophys. Res., 89 , 1055310569.

  • Wolanski, E., T. Asaeda, A. Tanaka, and E. Deleersnijder, 1996: Three-dimensional island wakes in the field, laboratory experiments and numerical models. Cont. Shelf Res., 16 , 14371452.

    • Search Google Scholar
    • Export Citation
  • Xie, S. P., W. T. Liu, Q. Liu, and M. Nonaka, 2001: Far-reaching effects of the Hawaiian Islands on the Pacific ocean–atmosphere system. Science, 292 , 20572060.

    • Search Google Scholar
    • Export Citation
  • Zdravkovich, M. M., 1997: Flow around Circular Cylinders: A Comprehensive Guide through Flow Phenomena, Experiments, Applications, Mathematical Models, and Computer Simulations. Oxford University Press, 694 pp.

    • Search Google Scholar
    • Export Citation
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Island Wakes in Deep Water

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  • 1 Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, California
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Abstract

Density stratification and planetary rotation distinguish three-dimensional island wakes significantly from a classical fluid dynamical flow around an obstacle. A numerical model is used to study the formation and evolution of flow around an idealized island in deep water (i.e., with vertical island sides and surface-intensified stratification and upstream flow), focusing on wake instability, coherent vortex formation, and mesoscale and submesoscale eddy activity. In a baseline experiment with strong vorticity generation at the island, three types of instability are evident: centrifugal, barotropic, and baroclinic. Sensitivities are shown to three nondimensional parameters: the Reynolds number (Re), Rossby number (Ro), and Burger number (Bu). The dependence on Re is similar to the classical wake in its transition to turbulence, but in contrast the island wake contains coherent eddies no matter how large the Re value. When Re is large enough, the shear layer at the island is so narrow that the vertical component of vorticity is larger than the Coriolis frequency in the near wake, leading to centrifugal instability on the anticyclonic side. As Bu decreases the eddy size shrinks from the island breadth to the baroclinic deformation radius, and the eddy generation process shifts from barotropic to baroclinic instability. For small Ro values, the wake dynamics is symmetric with respect to cyclonic and anticyclonic eddies. At intermediate Ro and Bu values, the anticyclonic eddies are increasingly more robust than cyclonic ones as Ro/Bu increases, but for large Re and Ro values, centrifugal instability weakens the anticyclonic eddies while cyclonic eddies remain coherent.

Corresponding author address: Dr. Changming Dong, IGPP, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1567. Email: cdong@atmos.ucla.edu

Abstract

Density stratification and planetary rotation distinguish three-dimensional island wakes significantly from a classical fluid dynamical flow around an obstacle. A numerical model is used to study the formation and evolution of flow around an idealized island in deep water (i.e., with vertical island sides and surface-intensified stratification and upstream flow), focusing on wake instability, coherent vortex formation, and mesoscale and submesoscale eddy activity. In a baseline experiment with strong vorticity generation at the island, three types of instability are evident: centrifugal, barotropic, and baroclinic. Sensitivities are shown to three nondimensional parameters: the Reynolds number (Re), Rossby number (Ro), and Burger number (Bu). The dependence on Re is similar to the classical wake in its transition to turbulence, but in contrast the island wake contains coherent eddies no matter how large the Re value. When Re is large enough, the shear layer at the island is so narrow that the vertical component of vorticity is larger than the Coriolis frequency in the near wake, leading to centrifugal instability on the anticyclonic side. As Bu decreases the eddy size shrinks from the island breadth to the baroclinic deformation radius, and the eddy generation process shifts from barotropic to baroclinic instability. For small Ro values, the wake dynamics is symmetric with respect to cyclonic and anticyclonic eddies. At intermediate Ro and Bu values, the anticyclonic eddies are increasingly more robust than cyclonic ones as Ro/Bu increases, but for large Re and Ro values, centrifugal instability weakens the anticyclonic eddies while cyclonic eddies remain coherent.

Corresponding author address: Dr. Changming Dong, IGPP, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1567. Email: cdong@atmos.ucla.edu

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